The present invention relates to an electrical motor with a shaft on which a rotor is mounted and with a bearing unit by means of which the shaft is mounted rotatably. The present invention relates particularly to a permanent magnet generator as an electrical motor of this type.
Where electrical motors are concerned, it is usually necessary to exchange the bearing of the rotor at certain intervals. For this purpose, the rotor has to be supported on another component of the electrical motor or on a device intended specifically for this. In permanent magnet-excited electrical motors, the rotor adheres to the stator not only by gravity, but also by additional magnetic force, when the rotor is supported on the stator at the time of bearing exchange. Tremendous forces are then necessary in order to release the rotor from the stator again. This presents problems particularly with regard to wind power plants which possess relatively large generators.
Hitherto, and only in the case of separately excited asynchronous generators, a bearing change has been carried out with the aid of a lifting cylinder which is required for supporting and raising the rotor. The rotor is then deposited on the stator. Where permanent magnet generators are concerned, a bearing change of this type can scarcely be carried out in practice.